will vs be going to

[keannu]

My grammar book says 'will' is for the decision made at the time of speech, while 'be going to' is for a plan made before speech, but is the distinction so strict? I've asked a native speaker, and he said the two are interchangeable in any cases.

Will) A: Tom! You've left the water on
B: I'm sorry Mom, I'll turn it off
be going to)A: What a mess! Your room is too dirty
B: I know, I'm going to clean it tonight.

[Barb_D]

I don't observe much of a difference in most cases.

[keannu]

I don't observe much of a difference in most cases.

If what you said is the case, I mean, there's little difference in the two forms, then, where is this distinction from? A made-up one or a very slight difference in the perception of the two in native speakers' minds?
I'm just curious if I can tell my people(students or whoever) that you don't have to distinguish the two or you are free to use either of the two in any cases.

[philo2009]

I'm afraid that, if you wish your students to speak remotely natural English, you should indeed make a point of teaching the difference between the two constructions, as they are far from interchangeable in many cases!

Neither of B's answers, for instance, is idiomatic in:

A: So what are your plans for the weekend?
B: Oh, I'll go sailing with my brother on Sunday.

(--> I'm going (to go) sailing with my brother: 'will' alone is NOT used to express a planned future activity.)

A: Could somebody post this letter for me? I haven't got time.
B: Yes, I'm going to do it!

(--> I'll do it! 'Be going to' is NOT used to express a decision about future action made in response to a stated, or perceived, problem.)

[5jj]

I'm afraid that, if you wish your students to speak remotely natural English, you should indeed make a point of teaching the difference between the two constructions, as they are far from interchangeable in many cases!

Well, they may not be interchangeable with exactly the same shade of meaning, but it is very often possible to use either construction.

Neither of B's answers, for instance, is idiomatic in:

A: So what are your plans for the weekend?
B: Oh, I'll go sailing with my brother on Sunday.

(--> I'm going (to go) sailing with my brother: 'will' alone is NOT used to express a planned future activity.)

No, but it can still be used here. It may have the sense of an instant decision, in that it was not particularly pre-planned, but it is not unnatural.

A: Could somebody post this letter for me? I haven't got time.
B: Yes, I'm going to do it!

(--> I'll do it! 'Be going to' is NOT used to express a decision about future action made in response to a stated, or perceived, problem.)

No, but if B had already decided that they were going to take the letter for A, then it is a natural enough response.

[keannu]

I'm afraid that, if you wish your students to speak remotely natural English, you should indeed make a point of teaching the difference between the two constructions, as they are far from interchangeable in many cases!

Neither of B's answers, for instance, is idiomatic in:

A: So what are your plans for the weekend?
B: Oh, I'll go sailing with my brother on Sunday.

(--> I'm going (to go) sailing with my brother: 'will' alone is NOT used to express a planned future activity.)

A: Could somebody post this letter for me? I haven't got time.
B: Yes, I'm going to do it!

(--> I'll do it! 'Be going to' is NOT used to express a decision about future action made in response to a stated, or perceived, problem.)

In an American drama, when a burglar broke into a house, I don't remember clearly, the owner woman freaked out said "I'm going to call the police". She didn't seem to have made a plan in advance before the burglar's breaking in, So if what you said is true, there's no exception? Do native speakers always say that way?

The other day, I was in a pharmacy in Korea selling a candy, and a Korean mom and her mixed-blood son(with a white) came in, and she said to her son, "Are you gonna buy this candy?" Did the son already have a plan to buy a candy? I don't think so. Maybe the mom made a mistake being a Korean.

[philo2009]

Well, they may not be interchangeable with exactly the same shade of meaning, but it is very often possible to use either construction.No, but it can still be used here. It may have the sense of an instant decision, in that it was not particularly pre-planned, but it is not unnatural.No, but if B had already decided that they were going to take the letter for A, then it is a natural enough response.

The issue here is plainly not simple grammaticality, but naturalness/appropriateness in context. I beg to disagree with your comments regarding the examples cited.

Regarding the first, an 'instant decision' can hardly be construed as a reasonable/natural response to a question about plans.

Regarding the second, it seems highly implausible that B would have formulated a "plan" to perform the task in question before the need for its execution had even arisen!!

[5jj]

Regarding the first, an 'instant decision' can hardly be construed as a reasonable/natural response to a question about plans.
I feel that it is possible. It may well not be the most common, but it is, as I wrote, 'not unnatural'.

Regarding the second, it seems highly implausible that B would have formulated a "plan" to perform the task in question before the need for its execution had even arisen!!
I did not suggest that. I wrote, "No, but if B had already decided that they were going to take the letter for A, then it is a natural enough response". At the time of B's decision, their only knowledge was presumably that the letter would need to be posted at some time, by someone. B perhaps decided that they woukld post it, in order to spare A the effort of going out. If A were an elderly person and B a young one, this is reasonably likely.

5

[philo2009]

In an American drama, when a burglar broke into a house, I don't remember clearly, the owner woman freaked out said "I'm going to call the police". She didn't seem to have made a plan in advance before the burglar's breaking in, So if what you said is true, there's no exception? Do native speakers always say that way?

Let me try to explain: had the burglar said

"Oh dear, I need someone to call the police to come and arrest me...Do you think perhaps you could do it, as I'm busy robbing you and don't have time?"

she would, being a kind, helpful person, no doubt have responded

"Don't worry. I'll call the police!"

As the situation actually is, though, she is simply informing the burglar of the plan/intention she formulated the moment she became aware of his presence. How many minutes/seconds/nanoseconds before this point she actually arrived at her decision is quite immaterial!　

The other day, I was in a pharmacy in Korea selling a candy, and a Korean mom and her mixed-blood son(with a white) came in, and she said to her son, "Are you gonna buy this candy?" Did the son already have a plan to buy a candy? I don't think so. Maybe the mom made a mistake being a Korean.

No mistake as far as I can see. She is quite legitimately enquiring about his plan/intention at that moment in time regarding the purchase or otherwise of the item in question.

If, on the other hand, having e.g. come without her purse, she had needed him to buy a candy for her, she might well have said

"Will you please buy me that candy, son?"

to which her filial offspring would certainly have answered

"Of course I will, Mother dear! "

Is that any clearer for you?

[philo2009]

Regarding the first, ...question about plans.
I feel that it is possible..., 'not unnatural'.


Regarding the second, ... had even arisen!!
I did not ... reasonably likely.


Thank you for your comments, the grounds for my disagreement with which, however, have, I think, been sufficiently clearly stated.
I have nothing to add to my previous post.